(a) Field of the Invention
The present invention relates to a three-dimensional composite of nickel cobalt oxide/graphene on nickel foam as a high-performance electrode for supercapacitors and its preparation method.
(b) Description of the Related Art
A supercapacitor is an energy storage device for storing and supplying electrical energy by utilizing the capacitor behavior caused by an electrochemical reaction between an electrode and an electrolyte. Supercapacitors have superior energy density and power density than conventional electrolytic capacitor and secondary battery, respectively. They can store and supply a large quantity of energy quickly and therefore attracted considerable interest as a new concept of energy storage and power sources.
In general, a supercapacitor consists of electrode materials, current collector, an electrolyte, and a separator. Of these, the electrode material is the most important component and controls the overall electrochemical performance of the supercapacitor.
An ideal supercapacitor electrode material often requires many properties, including high specific surface area, well-controlled porosity, high electronic conductivity, desirable electroactive sites, high thermal and chemical stability, and low cost of raw materials and manufacturing.
Thus, far, considerable efforts have been made to develop a variety of active electrode materials for supercapacitors. Among them, transition metal oxides, which are known as pseudocapacitive materials, have attracted considerable attention. On the other hand, they often have low rate capability and poor stability, which hinders the rapid electron transport required for high charge/discharge rates.